Salmon crossing cracked dam using modified fish ladders

Engineers, fish biologists and construction teams who have scrambled to meet an April 15 deadline to devise a way to move the first of an expected 20,000 spring Chinook salmon over the fractured Wanapum Dam believe they have met their initial goals.

Construction workers have retrofitted the fish ladders at the dam, 150 miles from upstream spawning grounds in Methow Valley rivers and streams, with pumps and an exit flume, according to Thomas Stredwick, a spokesperson for the Grant County Public Utility District (PUD), which operates the dam.

As of last Thursday (April 17), 31 spring Chinook and 102 steelhead had successfully ascended one of the fish ladders at the dam, which has been retrofitted with extensions and a resting pool. Workers are still constructing a flume, which is expected to be completed this week, to give the fish a gradual descent into the reservoir.

The modifications are necessary because the water level in the reservoir was reduced 26 feet—too far for fish to jump—to allow engineers to examine a crack in the dam. They are still evaluating the fracture and how to address the problem.

Other provisions for the first of the 20,000 spring Chinook expected to return to spawn this year include trapping migrating fish at the Priest Rapids Dam, 19 miles further downstream, to ferry them past Wanapum by truck. Workers for the Washington Department of Fish and Wildlife (WDFW) began trapping a small handful of fish last week.

While biologists say this method could work to move the endangered spring Chinook—which can reach 1,500 per day at peak—they acknowledge that the much larger runs of summer Chinook, sockeye and steelhead, which begin in June and can include 12,000 fish per day, require functional fish ladders.

WDFW has eight tanker trucks to move the salmon, each capable of moving up to 1,500 fish a day, according to the state wildlife agency.

“But there simply aren’t enough trucks, trained personnel, or hours in the day to move the number of salmon we’re expecting later in the year,” said Jim Brown, WDFW’s regional director.

After passing through Wanapum, it takes the spring Chinook at least two more weeks before they traverse the last three dams and reach the Methow River, according to Charlie Snow, a fish biologist with WDFW.

Fish biologists have been worried not only about the impact on spring Chinook, but also about half-a-dozen other species of salmon, both endangered and non-listed, that return to the Methow, Twisp and Chewuch rivers and their tributaries to spawn.

If the fish don’t make it to their spawning grounds to lay eggs, it would have serious consequences for future generations, since females of most species lay between 3,000 and 7,000 eggs each.

The temporary solution for migrating fish became necessary after a horizontal fracture 65 feet long and up to 2 inches wide was found in a spillway pier at Wanapum Dam in late February, according to the Grant County PUD.